1. Field of the Invention
The present invention relates to a built-in straight mobile antenna and more particularly, to a built-in straight mobile antenna type dual band antenna, which improves hearing aid compatibility performance.
2. Description of the Related Art
Following popularity of the work mode of personal digital cellular system, the interference problem of the magnetic field of the radiation of cellular phones with the performance of hearing aids has become more and more serious. Many hearing aid users complain the interference of their cellular telephones with their hearing aids. This problem has seized the attention of cellular telephone manufacturers, network service providers, hearing aid manufacturers and some other organizations.
Federal Communications Commission (FCC) has passed a set of hearing aid compatibility rules designed to make mobile phones more accessible to persons with disabilities. The FCC created a rating system to help consumers with hearing disabilities find a phone that will work with their hearing aids. In order not to interfere with the use of a hearing aid, FCC requires cellular telephone manufacturers to control magnetic interference below a certain level. FCC also requires cellular telephone manufacturers to provide certain models that provide a telecoil coupling function to transmit audio frequency to the hearing aid.
FCC raised the aforesaid request just because cellular telephones are going to disappear from the market. FCC indicated that analog cellular telephones are fully compatible to hearing aids, and requested that every cellular telephone manufacturer must prepare at least two models for each system that satisfy hearing aid compatibility standards (for example, a GSM and CDMA cellular telephone manufacturer must prepare at least 4 models of cellular telephones with telecoil coupling function that satisfy hearing aid compatibility standards). Cell phone manufacturers and cell phone service providers were requested to have at least one half of the available models satisfy hearing air compatibility before Feb. 18, 2008—the day that the analog cellular network was turned off in the U.S.A. completing the switch to digital networks such as GSM. In consequence, ANSI (American National Standards Institute) established “ANSI C63.19” standards.
A regular mobile antenna does not satisfy HAC standards. Many HAC (Hearing Aid Compatibility) related designs have been created. Some HAC related cell phone structure, casing and metal layout patents are known for cell phone applications.
US20060140428 discloses a mobile wireless communications device for a user wearing an electronic hearing aid adjacent an ear of the user, which includes an upper housing and a lower housing being slidably connected together for sliding between a retracted position and an extended use position, and an antenna carried by the lower housing adjacent the bottom end thereof so that the hearing aid is further separated from the antenna when the upper and lower housings are in the extended use position to reduce undesired coupling from the antenna to the hearing aid.
US20070003088 discloses an electronic device, which comprises a ground plane with two opposed edges, an electrical component (second ground plane, a speaker or a telecoil) spaced from the ground plane and disposed so as to not overlie the point with respect to a major surface of the ground plane, and an antenna resonantly coupled to the ground plane, but not resonant with the second ground plane if present. Preferably, the conductor is RF shielded.
However, conventional built-in straight mobile antennas are still not perfect in HAC performance.